AS/NZS 5125.1 Appendix H Published for Heat Pump Water Heater MEPS Testing

Standards Australia has now published AS/NZS 5125.1:2014 Amd 1, Heat pump water heaters - Performance assessment, Part 1: Air source heat pump water heaters.

The amendment introduces the new Appendix H test method for air source heat pump water heaters. This is the standard expected to underpin minimum energy performance standards (MEPS) testing for heat pump water heaters under the Greenhouse and Energy Minimum Standards (GEMS) framework.

This is an important milestone for manufacturers, suppliers, laboratories, regulators, and incentive scheme participants preparing for the next phase of heat pump water heater compliance in Australia and New Zealand.

What Appendix H Does

Appendix H provides a laboratory test method for assessing heat pump water heater performance under controlled conditions. It is intended to produce consistent, comparable results that can be used by regulators and consumers to understand how products perform.

The test method measures:

Coefficient of performance (COP)
Maximum deliverable heated water volume
Reheat time
Recharge rate
Energy consumption under defined operating conditions

In simple terms, reheat time is the elapsed time for the water heater to recover after a draw-off, usually reported in minutes or hours. Recharge rate expresses how quickly the product can restore usable hot water capacity, usually reported in litres per hour (L/h). The two are related, but they describe different things: reheat time tells you how long recovery takes, while recharge rate tells you the rate of useful hot water recovery.

The COP result is the key regulatory output. Once GEMS requirements are confirmed, MEPS will be set against COP.

The other results, including reheat time and recharge rate, are expected to be informative only. They will be listed on the GEMS registry to help public consumers and industry compare products, but they are not expected to form part of the minimum performance threshold.

The 50°C Delivery Temperature Requirement

One of the most important details in Appendix H is the minimum delivery temperature used in the test.

For Appendix H testing, delivered hot water must remain at or above 50°C.

This is different from AS/NZS 4234 simulation, where the minimum useful hot water delivery temperature is 45°C.

That 5°C difference matters. Heat pump water heaters that have been optimised around AS/NZS 4234 modelling, incentive scheme performance, or lower control set points may not deliver the same apparent performance under Appendix H.

In practical terms, products with lower tank set points, narrow deadbands, smaller storage volumes, or control settings designed around a 45°C delivery threshold may show reduced deliverable hot water volume in Appendix H testing.

Manufacturers should review:

Tank set point temperatures
Compressor restart logic
Deadband settings
Boost element control behaviour
Delivered hot water volume above 50°C
Recovery strategy after a major draw-off

Control settings that work well for AS/NZS 4234 modelling may not be the best settings for Appendix H results. This does not necessarily mean the physical product must change, but it does mean the tested configuration should be reviewed carefully before laboratory testing.

What Results Will Be Published

The proposed GEMS framework is expected to use Appendix H results in two ways.

First, COP will be used for MEPS. Products will need to meet the minimum COP level set under GEMS once the legislation is confirmed.

The Decision Regulation Impact Statement (DRIS) has indicated that the MEPS level for COP measured under AS/NZS 5125.1 Appendix H will be equivalent to 60% energy savings under AS/NZS 4234 simulation. This is an important signal for manufacturers, but it is not yet confirmed until the GEMS legislation is finalised.

Second, the GEMS registry is expected to publish additional performance information such as reheat time and recharge rate. These values will help consumers, specifiers, and industry participants compare products beyond a single efficiency number.

This distinction is important. A product may meet the MEPS COP requirement but still have a slow reheat time or low recharge rate. Those values may not determine compliance, but they will be visible in the market.

What Is Still Waiting on GEMS

The publication of AS/NZS 5125.1 Appendix H does not, by itself, activate MEPS.

The next step is for the GEMS requirements to be confirmed through legislation. Until that happens, the final compliance date, MEPS COP level, registration requirements, and transitional arrangements are still to be confirmed.

Now that Appendix H has been published, the expected next steps are:

Regulators confirm the GEMS determination and supporting requirements
The MEPS COP level is formally set
Registration and evidence requirements are clarified
Laboratories begin testing products against the published Appendix H method
Manufacturers prepare product ranges for GEMS registration

The recent policy direction indicates that MEPS will be introduced as soon as practicable, but manufacturers should treat the GEMS legislation as the final trigger for mandatory compliance.

What Manufacturers Should Do Now

Manufacturers do not need to wait for the final GEMS legislation before preparing.

Now is the time to review product ranges, identify which models are likely to require GEMS registration, and assess how each product is expected to perform under Appendix H.

In particular, manufacturers should consider whether existing control settings are suitable for a test that requires delivered water at or above 50°C, rather than the 45°C threshold used in AS/NZS 4234 modelling.

Early predictive modelling can help identify potential issues before physical testing, including products that may have:

Lower-than-expected delivered volume above 50°C
Long reheat times after draw-off
Poor recharge rates relative to competitors
Control behaviour that reduces Appendix H performance
COP results that may sit close to the likely MEPS threshold

How EnergyAE Can Help

EnergyAE supports heat pump water heater manufacturers with AS/NZS 4234 modelling, incentive scheme registrations, compliance strategy, and preparation for the upcoming GEMS MEPS framework.

For Appendix H and MEPS preparation, we can assist with:

Product range review
Predictive Appendix H performance modelling
Control settings review
Pre-test optimisation
Laboratory testing project management
GEMS registration preparation once requirements are confirmed

Get in touch with us if you would like to discuss how AS/NZS 5125.1 Appendix H may affect your product range.